Issue 4951 - Restrict request headers in XMLHttpRequest.Also test Accept-Encoding with th…

lib/compat.js

Index: lib/compat.js
===================================================================
--- a/lib/compat.js
+++ b/lib/compat.js
@@ -292,16 +292,51 @@ XMLHttpRequest.prototype =
   _loadHandlers: null,
   _errorHandlers: null,
   onload: null,
   onerror: null,
   status: 0,
   readyState: 0,
   responseText: null,
 
+  // list taken from https://developer.mozilla.org/en-US/docs/Glossary/Forbidden_header_name
+  _forbiddenRequestHeaders: {
+    "accept-charset": true,
+    "accept-encoding": true,
+    "access-control-request-headers": true,
+    "access-control-request-method": true,
+    "connection": true,
+    "content-length": true,
+    "cookie": true,
+    "cookie2": true,
+    "date": true,
+    "dnt": true,
+    "expect": true,
+    "host": true,
+    "keep-alive": true,
+    "origin": true,
+    "referer": true,
+    "te": true,
+    "trailer": true,
+    "transfer-encoding": true,
+    "upgrade": true,
+    "via": true,
+  },
+  _forbiddenRequestHeadersRe: new RegExp("^(Proxy|Sec)-", "i"),
+
+  _isRequestHeaderAllowed: function(header)
+  {
+    if (this._forbiddenRequestHeaders.hasOwnProperty(header.toLowerCase()))
+      return false;
+    if (header.match(this._forbiddenRequestHeadersRe))
+      return false;
+
+    return true;
+  },
+
   addEventListener: function(eventName, handler, capture)
   {
     var list;
     if (eventName == "load")
       list = this._loadHandlers;
     else if (eventName == "error")
       list = this._errorHandlers;
     else
@@ -375,17 +410,20 @@ XMLHttpRequest.prototype =
   {
   },
 
   setRequestHeader: function(name, value)
   {
     if (this.readyState > 1)
       throw new Error("Cannot set request header after sending");
 
-    this._requestHeaders[name] = value;
+    if (this._isRequestHeaderAllowed(name))
+      this._requestHeaders[name] = value;
+    else
+      console.warn("Attempt to set a forbidden header was denied: " + name);
   },
 
   getResponseHeader: function(name)
   {
     name = name.toLowerCase();
     if (!this._responseHeaders || !this._responseHeaders.hasOwnProperty(name))
       return null;
     else